Compact Dual-frequency Antenna Research Articles

Experiments of Microwave Ablation Based on Dual-Frequency Antenna Under Pulsed Mode

In this letter, we review the microwave ablation (MWA) under pulsed wave (PW) mode and perform the experiments by using a dual-frequency antenna. Parameters such as frequency (915 MHz or 2450 MHz), excitation power (40 W or 60 W), duty cycle (40%–60%), cycle (10 ms–100 s), and durations (5 min or 10) min are variably combined in different experimental schemes for investigation. Based on the results of these experiments, which use our super compact dual-frequency antenna and egg white as a reference tissue environment, it can be seen that PW MWA may reduce backward heating and increase ablation roundness to 0.964 (compared to a traditional continuous wave (CW) ablation roundness of 0.5). For further verification of these results and for comparison, a single-frequency antenna is also used under PW mode and the achieved ablation roundness is 0.91, which is also greater than that of 0.55 under CW mode. PW MWA can thus be considered as an effective candidate for tissue ablation during the treatment of tumors.

Compact Dual-Frequency Antenna Array With Large Frequency Ratio

A dual-fed dual-frequency shared-aperture antenna array with a large frequency ratio is investigated. Its unit cell consists of a microwave ground-surrounded patch antenna and a millimeter-wave substrate-integrated 2×2 slot antenna subarray. The former is excited in the fundamental TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode, whereas the slot elements are excited in their fundamental mode. Based on the dual-frequency antenna unit, a dual-frequency antenna array is designed. To demonstrate the idea, a prototype that consists of a C-band 2×2 patch antenna array and a Ka-band 8×8 slot antenna array was designed, fabricated, and tested. Its matching and radiation characteristics are studied for both bands. Reasonable agreement between the measured and simulated results is observed. Excellent measured intraband isolations of over 32 dB are obtained.

Wideband Dual-Frequency Antenna With Large Frequency Ratio

This communication investigates a new type of compact dual-frequency antenna, which is realized by using a single rectangular dielectric block with a groove along its center. It integrates a microwave dielectric resonator antenna (DRA) with a millimeter-wave Fabry–Perot resonator antenna (FPRA). The DRA is fabricated out of a dielectric block, excited by a vertical conducting strip on its side wall. The FPRA is realized by sticking the adhesive copper tape on the surfaces of the groove, forming a pair of parallel plates and the ground plane. The FPRA is excited by a sleeve-integrated L-probe, which suppresses the cross-polar fields and widens the bandwidth of the FPRA. To validate the idea, a dual-frequency antenna, covering both the 2.4 and 24 GHz ISM bands, was designed and measured. The DRA operates in its TEx111 mode, whereas the FPRA operates in its fundamental mode. Next, a wideband dual-frequency antenna was designed to further cover the 4G and future 5G frequency bands. Both of the TEx111 and TEx113 modes of the DRA are excited, broadening the bandwidth in the microwave band. Also, the FPRA mode and two L-probe modes are simultaneously excited to increase the bandwidth in the millimeter-waveband. The S-parameters, radiation patterns, antenna gains, and antenna efficiencies of the dual-frequency antennas are studied in detail. Reasonable agreement between the measured and simulated results is observed.

Dual-Frequency Folded-Parallel-Plate Antenna With Large Frequency Ratio

This communication investigates a new compact dual-frequency antenna with a large frequency ratio, which consists of a pair of folded parallel plates. It integrates the microwave parallel-plate waveguide resonator antenna (WRA) with the millimeter-wave Fabry-Perot resonator antenna (FPRA), with their resonant frequencies independent of each other. Due to the folded structure, the profile of the proposed antenna is lower than that of the conventional parallel-plate WRA. The WRA part is excited by a hook-shaped strip on its top, whereas the FPRA is excited by an L-probe with a half-ring sleeve. To demonstrate the idea, a dual-frequency antenna that covers the 2.4- and 24-GHz ISM bands was designed. ANSYS HFSS was used to simulate the S-parameters, radiation pattern, and antenna gain and reasonable agreement between the measured and simulated results is obtained.

Design of compact dual-frequency antenna with bandwidth enhancement

A compact dual-frequency antenna with enhanced bandwidth is proposed in this paper. Dual-frequency operation is realized by cutting a slot in the elliptical patch, and bandwidth enhancement is achieved by using a partial ground plane. Compared with the conventional half-wave antenna, the antenna has a compact size of 24 × 20 mm2, which equals to 0.38 λ1× 0.31 λ1(λ1, the guided wavelength at the first resonant frequency). The dual-frequency antenna with a partial rectangle ground and a partial arc-shaped ground is investigated for impedance matching. Simulated results indicate that the antenna with a partial arc-shaped ground can obtain a larger bandwidth for two bands than that with a partial rectangle ground. Experimental results show that the antenna with a partial arc-shaped ground can operate in 2.4 and 5 GHz bands, which covers the 2.4, 5.2 and 5.8 GHz for wireless local area network. The impedance bandwidths of two bands are 9.5 and 13.6%, respectively. Also, good radiation performances have been achieved at two bands.

Design and transmission line model analysis of a compact dual-frequency antenna

In this study, a compact dual-frequency antenna with stacked configuration is proposed, and the transmission line model for the antenna is also studied. Compared with the conventional stacked dual-frequency antenna, the radiating element with half-guided wavelength at the first resonant frequency is arranged on two layers connected through one via hole, thus the dimension of the antenna can be reduced effectively. Each patch of the antenna is modelled as a section of transmission line terminated by two radiating slots, and a via hole between stacked patches is represented by an inductor and a capacitor in parallel. In particular, the formula for the capacitor of a via hole between stacked patches is provided when the antenna is fed from the upper patch. To validate the transmission line model, two compact dual-frequency antennas are designed and fabricated. The results of simulations and measurements indicate that the proposed transmission line model is suitable for analysing compact dual-frequency antennas with stacked configuration.

Parametric Design of Compact Dual-Frequency Antennas for Wireless Sensor Networks

A parametric study for the design of a planar compact dual-frequency antenna is presented. The proposed geometry and the suggested tailoring procedure provide a useful template for generating a single antenna able to serve as bidirectional node for a generic Wireless Sensor Network within the UHF and microwave frequency bands. The constructive parameters can be set to adapt the radiating device for different unlicensed bands and to comply with the international radiation power regulations. A careful design procedure will be described to tune the antenna template for working at the required frequencies. In order to prove the effectiveness of the suggested approach as well as the reliability of the adopted technique, comparisons between simulations and measurements of realized prototypes will be reported.

Compact dual-frequency linear antenna with partial ground plane

In order to meet the need of multiband and antenna-in-package (AiP), a compact dual-frequency antenna with a partial ground and linear structure is proposed, optimised and realised. The proposed antenna was designed at 2.4 GHz and 5.8 GHz bands for WLAN applications. The total size of the antenna is 20 mm × 20 mm, equals to 0.27 λg1 × 0.27 λg1 and 0.65 λg2 × 0.65 λg2 (λg1, λg2 are the microstrip (with ground) guiding wavelengths at 2.4 GHz and 5.8 GHz) or 0.15 λ01 × 0.15 λ01 and 0.38 λ02 × 0.38 λ02 (λ01, λ02 are the wavelengths in the atmosphere at 2.4 GHz and 5.8 GHz). Also, omnidirectional radiation characteristics in the desired bands can be obtained.

CPW-fed compact meandered patch antenna for dual-band operation

By inserting a meandering slit at the edge of a rectangular patch printed in a single layer and fed by a coplanar waveguide (CPW) transmission line, a novel compact dual-frequency antenna is obtained. The designed antenna, with, including ground plane, only 20 mm in height and 30 mm in width, can operate at both 2.0 and 5.32 GHz bands and provide sufficient bandwidths for the UMTS and WLAN systems, respectively.